The throughput performance of a slotted, non-persistent Idle-Signal Casting Multiple Access (ICMA) protocol under the effects of various combinations of Rayleigh fading, lognormal shadowing, and spatial distribution of mobile users is studied. The opposing effects of propagation impairments on the performance of the protocol through simultaneously increasing the probability of receiver capture and attenuation of the received signal power level are demonstrated.

This paper proposes a dynamically randomized version of DES (called RDES) in which a input-dependent swapping Sk(X) is added onto the right half of the input in each round of DES. This new scheme decreases the probability of success in differential cryptanalysis because it decreases the characteristic probability. Each "best" two-round characteristic probability is analyzed for typical schemes of the RDES: (i) RDES-1 with a simple one-level swapping, (ii) RDES-1' with an optimal one-level swapping, (iii) RDES-2 with a simple two-level swapping, and (iv) RDES-2' with an optimal two-level swapping. The main results are as follows. (a) The differential attacks on the 16-round RDES-1' and the 16-round RDES-2 require more computational time than the exhaustive search. (b) A differential attack is substantially inapplicable to the 16-round RDES-2' because more than 263 chosen plaintext pairs are required. (c) The encryption/decryption speed of the n-round RDES is almost the same as that of the n-round DES.

This paper proposes and investigates an intelligent error-controlling scheme according to different importance of segmental information. In particular, the scheme is designed for facial images encoded by model-based coding that is a kind of intelligent compression coding. Intelligent communication systems regard the contents of information to be transmitted with extremely high compression and reliability. After highly efficient information compression by model-beaed coding, errors in the compressed information lead to severe semantic errors. The proposed scheme reduces semantic errors of information for the receiver. In this paper, we consider Action Unit (AU) as a segment of model-based coded facial image of human being and define the importance for each AU. According to the importance, an AU is encoded by an appropriated code among codes with different error-correcting capabilities. For encoding with different error controlling codes, we use three kinds of constructions to obtain unequal error protection (UEP) codes in this paper. One of them is the direct sum construction and the others are the proposed constructions which are based on joint and double coding. These UEP codes can have higher coderate than other UEP codes when minimum Hamming distance is small. By using these UEP codes, the proposed intelligent error-controlling scheme can protect information in segment in order to reduce semantic errors over a conventional error-controlling scheme in which information is uniformly protected by an error-correcting code.

The byte error locating codes specify the byte location in which errors are occurred without indicating the precise location of erroneous bit positions. This type of codes is considered to be useful for fault isolation and reconfiguration in the fault-tolerant computer systems. In this paper, difference between the code function of error-location and that of error-correction/error-detection is clarified. With using the concepts of unidirectional byte distance, unordered byte number and ordered byte number, the necessary and sufficient conditions of the unidirectional byte error locating codes are demonstrated.

A polarity-convertible driver is necessary as a basic component of several Josephson random access memories. This driver must be able to inject a current having positive or negative polarity into a load transmission line such as a word or bit line of the RAM. In this paper, we propose a resistor coupled Josephson polarity-convertible driver which is highly sensitive to input signals and has a wide operating margin. The driver consists of several Josephson junctions and several resistors. The input signal is directly injected to the driver through the resistors. The circuit design is discussed on the operating principle of the driver. The driver is fabricated by 1.5 µm Nb technology with Nb/AlOx/Nb Josephson junctions, two layer Nb wirings, an Nb ground plane, Mo resistors, and SiO2 insulators. The Nb/AlOx/Nb Josephson junctions are fabricated using technology refined for sub-micron size junctions. The insulators between wirings are formed using bias sputtering technique to obtain good step coverage. The driver circuit size is 53 µm34 µm. Measurements are carried out at 10 kHz to quasistatically test the polarity-convertible function and the operating margin of the driver. Proper polarity-convertible operation is confirmed for a large operating bias margin of 70% at a fairly small input current of 0.3 mA.

In computer vision, the interpretation of 3D motion of an object in the physical world is an important task. This study proposes a 3D motion interpretation method which uses a neural network system consisting of three kinds of neural networks. This system estimates the solutions of 3D motion of an object by interpreting three optical flow (OF-motion vector field calculated from images) patterns obtained at the different view points for the same object. In the system, OF normalization network is used to normalize diverse OF patterns into the normalized OF format. Then 2D motion interpretation network is used to interpret the normalized OF pattern and to obtain the object's projected motion onto an image plane. Finally, 3D motion interpretation network totally interprets the three sets of the projected motions and it derives the solutions of the object's 3D motion from the inputs. A complex numbered version of the back-propagation (Complex-BP) algorithm is applied to OF normalization netwerk and to 2D motion interpretation network, so that these networks can learn graphical patterns as complex numbers. Also a 3D vector version of the back-propagation (3DV-BP) algorithm is applied to 3D motion interpretation network so that the network can learn the spatial relationship between the object's 3D motion and the corresponding three OF patterns. Though the interpretation system is trained for only basic 3D motions consisting of a single motion component, the system can interpret unknown multiple 3D motions consisting of several motion components. The generalization capacity of the proposed system was confirmed using diverse test patterns. Also the robustness of the system to noise was probed experimentally. The experimental results showed that this method has suitable features for applying to real images.

A method is presented for computing the number of codewords of weight less than or equal to a given integer in a binary block code by using its trellis diagram. The time and space complexities are analyzed. It is also shown that this method is very efficient for the codes which have relatively simple trellis diagram, say some BCH codes. By using this method, the weight distribution of (128,36) extended BCH code is computed efficiently.

A new recursive method for obtaining the mean waiting time in a polling system with general service order and gated service discipline is proposed. The analytical approach used to obtain the mean waiting time is via an imbedded Markov chain and a new recursive method is used to obtain the moments of pseudocycle time which are parameters in the formula for the mean waiting time. This method is computationally tractable, so the analytical results can cover a wide range of applications. Simulations are also conducted to verify the validity of the analysis.

Recently there has been considerable interest in coded modulation schemes that offer multiple levels of error protection. That is, constructions of (block or convolutional) modulation codes in which signal sequences associated with some message symbols are separated by a squared Euclidean distance that is larger than the minimum squared Euclidean distance (MSED) of the code. In this paper, the trellis structure of linear unequal-error-protection (LUEP) codes is analyzed. First, it is shown that LUEP codes have trellises that can be expressed as a direct product of trellises of subcodes or clouds. This particular trellis structure is a result of the cloud structure of LUEP codes in general. A direct consequence of this property of LUEP codes is that searching for trellises with parallel structure for a block modulation code may be useful not only in analyzing its structure and in simplifying its decoding, but also in determining its UEP capabilities. A basic 3-level 8-PSK block modulation code is analyzed under this new perspective, and shown to offer two levels of error protection. To illustrate the trellis structure of an LUEP code, we analyze a trellis diagram for an extended (64,24) BCH code, which is a two-level LUEP code. Furthermore, we introduce a family of LUEP codes based on the |||-construction, using Reed-Muller (RM) codes as component codes. LUEP codes in this family have the advantage of having a well known trellis structure. Their application in constructing LUEP-QPSK modulation codes is presented, and their error performance over an AWGN channel examined.

We analyze the error probability performance of multi-pulse pulse position modulation (MPPM) in noisy photon counting channel. Moreover we investigate the error perofrmance of convolutional coded MPPM and RS coded MPPM in noisy photon counting channel. We define a distance between symbols as the number of nonoverlapping pulses in one symbol, and by using the distance we analyze the error performance of MPPM in noisy photon counting channel. It is shown that MPPM has better performance than PPM in the error probability performance in noisy photon counting channel. For PPM in noisy photon counting channel, convolutional codes are more effective than RS codes to reduce the average transmitting power. For MPPM in noisy photon counting channel, however, RS codes are shown to be more effective than convolutional codes.

A specific signal in most of actual environmental systems fluctuates complicatedly in a non-Gaussian distribution form, owing to various kinds of factors. The nonlinearity of the system makes it more difficult to evaluate the objective system from the viewpoint of internal physical mechanism. Furthermore, it is very often that the reliable observation value can be obtained only within a definite domain of fluctuating amplitude, because many of measuring equipment have their proper dynamic range and the original random wave form is unreliable at the end of amplitude fluctuation. It becomes very important to establish a new signal processing or an evaluation method applicable to such an actually complicated system even from a functional viewpoint. This paper describes a new trial for the signal processing along the same line of the extended regression analysis based on the Bayes' theorem. This method enables us to estimate the response probability property of a complicated system in an actual situation, when observation values of the output response are saturated due to the dynamic range of measuring equipment. This method utilizes the series expansion form of the Bayes' theorem, which is applicable to the non-Gaussian property of the fluctuations and various kinds of correlation information between the input and output fluctuations. The proposed method is newly derived especially by paying our attention to the statistical information of the input-output data without the saturation operation instead of that on the resultantly saturated observation, differing from the well-known regression analysis and its improvement. Then, the output probability distribution for another kind of input is predicted by using the estimated regression relationship. Finally, the effectiveness of the proposed method is experimentally confirmed too by applying it to the actual data observed for indoor and outdoor sound environments.

Broadcasting with secrecy of messages is important in a situation such as pay television. In pay television only a broadcasting station broadcasts a message. On the other hand, broadcast communication is also important. Broadcast communication means any user in a whole group can broadcast a message to any subset of the group. In this paper the efficiency of secure broadcast communication is discussed in terms of the length of messages sent and the encryption speed. We prove that the length of the broadcast messages is not kept less than O(n), where n is the number of receivers, when a broadcast system has a form of a single system which is defined as the generalized form of an individual key method and a master key method. In contrast, the proposed secure broadcast communication method, a multi-dimension method, keeps the length of messages sent O(mmn), where m is the number of the dimension used in the multi-dimension method. At the same time the encryption speed was reduced from O(n(log(n+C2)+C3)) of the master key method to O(mn(logmn+C1)) of the multi-dimension method.

This paper proposes RSA-type cryptosystems over elliptic curves En(O, b) and En(a, O),where En(a, b): y2 x3+ax+b (mod n),and n is a product of from-free primes p and q. Although RSA cryptosystem is not secure against a low exponent attack, RSA-type cryptosystems over elliptic curves seems secure against a low multiplier attack. There are the KMOV cryptosystem and the Demytko cryptosystem that were previously proposed as RSA-type cryptosystems over elliptic curves. The KMOV cryptosystem uses form-restricted primes as p q 2(mod 3)or p q 3(mod 4), and encrypts/decrypts a 2log n-bit message over varied elliptic curves by operating values of x and y coordinates. The Demytko cryptosystem, which is an extension of the KMOV cryptosystem, uses form-free primes, and encrypts/decrypts a log n-bit message over fixed elliptic curves by operating only a value of x coordinates. Our cryptosystems, which are other extensions fo the KMOV cryptosystem, encrypt/decrypt a 2log n-bit message over varied elliptic curves by operating values of x and y coordinates. The Demytko cryptosystem and our cryptosystems have higher security than the KMOV cryptosystem because from-free primes hide two-bit information about prime factors. The encryption/decryption speed in one of our cryptosystems is about 1.25 times faster than that in the Demytko cryptosystem.

Recently, a lot of research works have been carried out regarding intelligent communication. If the final information sink is assumed as a human being, a communication channel can be used more effectively when encoders/decoders work "intelligently" or take into account of the semantics of information to be sent. We have been studying error-controlling systems based on different importance of segmental information. The system divides the information input into segments to which individual importance can be assigned. The segments are individually encoded by appropriate error-correcting codes (ECCs) which correspond to their importance among codes with different error-correcting capabilities. For the information that difference of the importance is systematically aligned, conventional UEP (unequal error protection) codes can be applied, but we treat the case that alignment of the importance of the information source is not systematically aligned. Since the system uses multiple ECCs with different (n,k,d) parameters, information regarding what length of the next codeword is required for decoding. We propose error controlling schemes using mulriple ECCs; the first scheme and the second scheme use the obvious codelength identifying information. In the second scheme, information bits are sorted so that segments with the same importance can be encoded by an ECC with the same error-correcting capability. The third scheme is a main proposal in this paper and uses Variable Capability Coding scheme (VCC) which uses some ECCs having different error-correcting capabilities and codelengths. A sequence encoded by the VCC is separable into appropriate segments without obvious codelength identifying information when the channel error probability is low. Subsequently, we evaluate these schemes by coderate when (1) error correcting capability (2) codelength identifying capability are the same. One of the feature of VCC is the capability of resuming from propagative errors because errors beyond the codelength identifying capability occur and the proper beginning of the codeword is lost in the decoder. We also evaluate this capability as (3) resynchronizing capability.

In the actual acoustic environment, the stochastic process exhibits various non-Gaussian distribution forms, and there exist potentially various nonlinear correlations in addition to the linear correlation between time series. In this study, a nonlinear ARMA model is proposed, based on the Bayes' theorem, where no artificially pre-established regression function model is assumed between time series, while reflecting hierarchically all of those various correlation informations. The proposed method is applied to the actual data of road traffic noise and its practical usefulness is verified.

This paper describes highly parallel analog image coding and decoding by cellular neural networks (CNNs). The communication system in which the coder (C-) and decoder (D-) CNNs are embedded consists of a differential transmitter with an internal receiver model in the feedback loop. The C-CNN encodes the image through two cascaded techniques: structural compression and halftoning. The D-CNN decodes the received data through a reconstruction process, which includes a dynamic current distribution, so that the original input to the C-CNN can be recognized. The halftoning serves as a dynamic quantization to convert each pixel to a binary value depending on the neighboring values. We approach halftoning by the minimization of error energy between the original gray image and reconstructed halftone image, and the structural compression from the viewpoints of topological and regularization theories. All dynamics are described by CNN state equations. Both the proposed coding and decoding algorithms use only local image information in a space inveriant manner, therefore errors are distributed evenly and will not introduce the blocking effects found in DCT-based coding methods. In the future, the use of parallel inputs from on-chip photodetectors would allow direct dynamic quantization and compression of image sequences without the use of multiple bit analog-to-digital converters. To validate our theory, a simulation has been performed by using the relaxation method on an 150 frame image sequence. Each input image was 256256 pixels whth 8 bits per pixel. The simulated fixed compression rate, not including the Huffman coding, was about 1/16 with a PSNR of 31[dB]35[dB].

This papter proposes a new type of unidirectional error control codes which indicates the location of unidirectional errors clustered in b-bit length, i.e., unidirectional byte error in b (b2) bits. Single unidirectional b-bit byte error locating codes, called SUbEL codes, are first clarified using necessary and sufficient conditions, and then code construction algorithm is demonstrated. The lower bound on check bit length of the SUbEL codes is derived. Based on this, the proposed codes are shown to be very efficient. Using the code design concept presented for the SUbEL codes, it is demonstrated that generalized unidirectional byte error locating codes are easily constructed.

This paper presents new go-back-N ARQ protocols for point-to-multipoint communications over broadcast channels such as satellite or broadcast radio channels. In the conventional go-back-N ARQ protocols for multidestination communications, usually only error detection codes are used for error detection and m copies of a frame are transmitted at a time. In one of our protocols, a bit-by-bit majority-voting decoder based on all of the m copies of a frame is used to recover the transmitted frame. In another protocol, a hybrid-ARQ protocol, which is an error detection code concatenated with a rate repetition convolutional code with the Viterbi decoding, is used. In these protocols, a dynamic programming technique is used to select the optimal number of copies of a frame to be transmitted at a time. The optimal number is determined by round trip propagation delay of the channel, the error probability, and the number of receivers that have not yet received the message. Analytic expressions are derived for the throughput efficiency of the proposed protocols. The proposed point-to-multipoint protocols provide satisfactory throughput efficiency and perform considerably better than the conventional protocols under high error rate conditions, especially in environments with a large number of receivers and large link round trips. In this paper we analyze the performances of the proposed protocols upon the random error channel conditions.

The techniques for imaging optically opaque region using an electromagnetic wave radar are being developed. One important application of these techniques is the detection of buried pipes and cables. The image quality of subsurface radar often becomes low because the electromagnetic waves are affected by the attenuation and inhomogeneity of soil. Hence, a method which improves the quality of the radar images has been required. The migration method is utilized in reflective seismic processing and is derived based on the solution of the wave equation represented in spatial frequency domain. It is classified into the F-K and the phase-shift (P-S) migration method. The former is derived on the assumption that propagation velocity of the wave is uniform in the soil while the latter is assumed that the propagation velocity is varying depending on the depth from the ground surface. The P-S method gives relatively good quality images but it requires very long computation time. In this paper, we propose the block migration method in which the F-K method is applied to the divided image blocks with local propagation velocity. In order to solve a problem concerning the connection between the contiguous blocks we present two approaches which are the processings using the overlapped regions and the Lapped Orthogonal Transform (LOT). Some experimental results point out that the block migration method has a good capability of improving the image quality and the processing time using LOT becomes one tenth in comparison with the P-S method.

Linear lightwave networks (LLNs) are optical networks in which network nodes perform only linear operations on optical signals: power splitting, combining, and non-regenerative amplification. While previous efforts on LLNs assume only one fiber per link, we consider a multi-fiber linear lightwave network (M-LLN) architecture for telecommunications where switching exchanges are normally connected by multi-fiber cables. We propose a class of linear path (LP) allocation schemes for establishing optical paths in M-LLNs, and show that they have a better performance than those proposed for single-fiber LLNs. We show that M-LLNs can be implemented with commercially available components, and discuss the implementation issues in detail.